Equipment is important but it's not the first thing to worry. You are doing great as it is. After decades of craving for it, I finally have a bag full of prime lenses but I realised that although they are amazing and help me a lot, they haven't change my photography itself at all.
That 100-400 sounds like a beast :)
Cheers!
I agree with his words, in the end one ends up using very little, although if you feel lucky to have the choice, the lighter your luggage is usually the better. Yes, it's really interesting, I haven't used it too much but I hope to do so soon. Thanks for stopping by, cheers